1. Field of the Invention
The present invention relates to semiconductor devices.
2. Description of the Related Art
Semiconductor devices receive input currents or output currents from outside and provide various specific functions in response. Semiconductors vary widely in their configurations. Typically, however, semiconductor devices incorporate therein a plurality of elements each constituting part of electric circuitry for achieving the specific functions as the semiconductor devices. In order to support these elements and provide electric continuity between these elements as well, metal lead frames are used. The number, shape and size of the lead frames are determined in accordance with the functions, shape and size of the elements. Once the elements are mounted on a lead frame, they are then covered with sealing resin. The sealing resin protects these elements and part of the lead frame as well. These semiconductor devices are then utilized as mounted on circuit substrates and so on, of electronic products for example.
The lead frames are often formed by punching a sheet of metal with a metal die for example. The method using a metal die has an advantage that it is capable of forming the lead frames efficiently and accurately. However, the lead frames vary considerably in its number, size and shape depending on the elements. Therefore, once there is a change in intended functions, for example, of the semiconductor device, the size and/or shape of the lead frame need be changed. This means that the metal die need be redesigned. Since the metal die is relatively expensive, this results in cost increase in the semiconductor device if the semiconductor device is manufactured only in a small quantity.
Another problem lies in the fact that the lead frame typically is a flat piece of metal since it is made from a sheet of metal. Although it is not impossible to make a three-dimensional shape by means of discretionary squeezing processes, there is a certain limit. For the semiconductor devices, there is a constant demand for a higher level of functionality and a wider range of multi-functionality. In order to meet these demands, high density mounting and three-dimensional layout of the elements will be necessary other than two-dimensional.
Patent Document: JP 2012-99673 A